Method for controlling a compressor system by computational minimization of the cut-off pressure, as well as control device and data set

Abstract

Method for controlling a compressor system (1) comprising a plurality of compressors (2), in particular of different designs and / or capacities, wherein the compressor system (1) is intended to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, where decisions are made at fixed or variable time intervals regarding switching operations to adapt the pressure fluid system to current conditions, that - in a pre-selection step (10), taking into account the current conditions, switching alternatives (13) are excluded from the multitude of combinatorially available switching alternatives (13), - in a main selection step (11) remaining switching alternatives (13) are weighed against each other using one or more optimization criteria and optimal switching alternatives (13) are selected under the given criteria and - in a control step (12) the selected switching alternative (13) is output for implementation in the compressor system (1) characterized by that the control of the system (1) takes measures to increase the generation of compressed pressure fluid when a potentially variable switch-on pressure (102) is reached and measures to reduce the generation of compressed pressure fluid when a potentially variable switch-off pressure (103) is reached, wherein The optimal cut-off pressure (103) is determined by computationally minimizing the quotient of the total work loss in a predefined periodic time interval relating to a switching alternative (13) and the time interval itself, wherein the total work loss includes the sum of the work loss of all load-running compressors (2) in the time interval, the idle work loss of all compressors (2) to be switched on in the time interval, and the switching work loss of all compressors (2) to be switched on and off in the time interval.

Description

[0001] The invention relates to a method for controlling a compressor system comprising a plurality of compressors, in particular of different designs and / or capacities. The invention also relates to a control device for such a compressor system and to a data set for controlling such a compressor system.

[0002] Compressor systems, especially those intended for industrial applications, typically require a large number of individual compressors to supply sufficient pressure fluid. To operate such a system efficiently, the economic viability of individual components and the entire system is increasingly considered not only during the design and planning phases but also during operation. These economic aspects are typically considered alongside environmental regulations and quality requirements. The energy consumption of a compressor system can account for up to 80% of the total operating costs, making energy consumption the primary cost factor for compressor system operators.

[0003] To utilize the energy-saving potential of a compressor system, measures such as heat recovery and leakage reduction have been implemented. It has also been recognized that the use of suitable control systems can significantly reduce operating costs. Controlling the compressor system allows for the appropriate distribution of operating times among different compressors, thereby reducing the risk of failure and simplifying maintenance. For example, if a compressor fails, the control system can activate other compressors that are idling or at a standstill and instruct them to supply pressurized fluid to prevent a drop in the operating pressure or a complete shutdown of the compressor system.

[0004] In the simplest case, cascade or pressure band controls are used to manage compressor systems comprising multiple compressors. These controls determine which compressor in the system is switched on or off under predetermined operating conditions. With cascade control, each compressor is assigned a specific pressure range, according to which the control system determines whether a particular compressor is switched on or off. By defining individual pressure ranges, also called pressure bands, assigned to the compressors, the required amount of pressurized fluid can be met even at high consumption rates by switching on a larger number of compressors or by switching on compressors with a higher delivery rate of pressurized fluid compared to the others. However, a disadvantage of such controls is that they typically do not take into account the actual consumption of pressurized fluid.The change in the current pressure fluid sampling is taken.

[0005] Advanced pressure band controls utilize the possibility of controlling any number of compressors via a single pressure band. This control method allows for the reduction of the maximum pressure of the pressurized fluid in the compressor system, while simultaneously minimizing some energy losses within the system.

[0006] Nevertheless, it has been shown that pressure band controls are not suitable for controlling a compressor system in such a way that the pressure fluid demand is met both adequately and in an energy-efficient manner, given the typical staggered operation of individual compressors and fluctuating pressure fluid withdrawal from the compressor system. For example, operating conditions or constellations can occur in the compressor system that lead either to an insufficient supply of pressure fluid or to an extremely energy-inefficient supply of pressure fluid.

[0007] EP 04 31 287 A1 discloses the shifting of operating points, which is carried out computationally in a simulation. However, the simulation does not take into account current conditions in the compressor system, but rather operates using stored data. DE 198 26 169 A1 aims to facilitate the integration of different units in a compressor system with regard to the control of the entire compressor system. Furthermore, conventional control methods for a compressor system are also known from DE 33 32 619 A1 and DE 102 08 676 A1.

[0008] Based on the above-described methods for controlling a compressor system, the task is therefore to propose an improved method for controlling a compressor system which enables a sufficient supply of pressure fluid even with fluctuating withdrawal of pressure fluid from the compressor system, while at the same time ensuring that the switching operations initiated by the control system are as economical as possible.

[0009] According to the invention, this problem is solved by a method for controlling a compressor system comprising a plurality of compressors, in particular of different designs and / or capacities, according to claims 1 and 2. Furthermore, the problem is solved by a control device for such a compressor system according to claims 23 and 24, and by a data set for controlling such a compressor system according to claims 25 and 26.

[0010] In particular, the problem underlying the invention is solved by a method for controlling a compressor system comprising a plurality of compressors, especially of different designs and / or capacities, wherein the compressor system is intended to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, wherein decisions regarding switching operations for adapting the pressure fluid system to current conditions are made at fixed or variable time intervals, wherein, in a pre-selection step, preferably taking into account the current conditions, switching alternatives are excluded from the multitude of combinatorially available switching alternatives.wherein in a main selection step remaining switching alternatives are weighed against each other using one or more optimization criteria and optimal switching alternatives are selected among the specified criteria, and wherein in a control step the selected switching alternative is output for implementation in the compressor system, wherein the control of the system takes measures to increase the generation of compressed pressure fluid when a possibly variable switch-on pressure is reached, and measures to reduce the generation of compressed pressure fluid when a possibly variable switch-off pressure is reached, wherein the optimal switch-off pressure is determined by computationally minimizing the quotient of the total work loss in a predefined periodic time interval relating to a switching alternative and the time interval itself,where the total energy loss includes the sum of the energy loss of all compressors running under load in the time interval, the idling energy loss of all compressors to be switched on in the time interval, and the switching energy loss of all compressors to be switched on and off in the time interval.

[0011] Furthermore, the problem is solved by a method for controlling a compressor system comprising a plurality of compressors, in particular of different designs and / or capacities, wherein the compressor system is to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, wherein the system control takes measures to increase the production of compressed pressure fluid upon reaching a potentially variable switch-on pressure and measures to reduce the production of compressed pressure fluid upon reaching a switch-off pressure, wherein the switch-off pressure is variable and changes depending on the current configuration of the compressor system and / or taking into account a defined switching action (a defined change in the configuration of the compressor system).wherein the optimal cut-off pressure is determined by computationally minimizing the quotient of the total work loss in a predefined periodic time interval relating to a switching alternative and the time interval itself, wherein the total work loss comprises the sum of the work loss of all load-running compressors in the time interval, the idle work loss of all compressors to be switched on in the time interval, and the switching work loss of all compressors to be switched on and off in the time interval.

[0012] Here and in the following, the maintenance of a predetermined overpressure should be carried out in such a way that a predetermined adaptation pressure, to be achieved by the actual pressure profile, is not undershot by the actual pressure profile or only insignificantly and / or briefly, and optionally an upper pressure limit is not exceeded or only insignificantly and / or briefly.

[0013] Furthermore, the inventive problem is solved by a control device for a compressor system comprising a plurality of compressors, in particular of different designs and / or capacities, wherein the compressor system is intended to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, wherein decisions regarding switching operations for adapting the pressure fluid system to current conditions are made at fixed or variable time intervals, and wherein the control device comprises: an exclusion device which, preferably taking into account the current conditions, excludes switching alternatives from the plurality of combinationally available switching alternatives, a selection device,The remaining switching alternatives are weighed against each other using one or more optimization criteria, and an optimal switching alternative is selected from among the given criteria, as well as an output device that is designed to output the selected switching alternative for implementation in the compressor system.

[0014] Furthermore, the problem underlying the invention is solved by a control device for a compressor system comprising a plurality of compressors, in particular of different designs and / or capacities, wherein the compressor system is intended to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, and wherein the control device comprises: A cut-off pressure determination device which, in the event of an overproduction of pressure fluid, determines a cut-off pressure depending on the current configuration of the compressor system and / or taking into account a defined switching action (a defined change in the configuration of the compressor system).

[0015] Furthermore, the inventive problem is solved by a data set, which is preferably configured for transmission in a data network or stored on data carriers, for controlling a compressor system, wherein the compressor system comprises a plurality of compressors, in particular of different designs and / or capacities, and wherein the compressor system is intended to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, wherein decisions regarding switching operations for adapting the pressure fluid system to current conditions are made at fixed or variable time intervals, such that in a preselection step, preferably taking into account the current conditions, switching alternatives are excluded from the multitude of combinatorially available switching alternatives.In a main selection step, the remaining switching alternatives are weighed against each other using one or more optimization criteria, and the optimal switching alternatives are selected from among the specified criteria. In a control step, the selected switching alternative is output for implementation in the compressor system.

[0016] Furthermore, the inventive problem is solved by a data set, which is preferably configured for transmission in a data network or stored on data carriers, for controlling a compressor system, wherein the compressor system comprises a plurality of compressors of, in particular, different designs and / or capacities, wherein the compressor system is intended to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, wherein the control system of the system takes measures to increase the generation of compressed pressure fluid when a potentially variable switch-on pressure is reached and measures to reduce the generation of compressed pressure fluid when a switch-off pressure is reached.where the cut-off pressure is variable and is changed depending on the current configuration of the compressor system and / or taking into account a defined switching action (a defined change in the configuration of the compressor system).

[0017] Here and in the following, the term "control" should also be understood in the sense of "regulation." Since the method for controlling a compressor system, as well as the individual embodiments of the method, can exhibit both control-specific and regulation-specific characteristics, a strict distinction between the two terms has been omitted here for the sake of clarity.

[0018] A key concept of the present invention is that, prior to implementing a switching action to adapt the pressure fluid system to current conditions, a multitude of possible switching alternatives are considered. These alternatives are then weighed against each other using one or more optimization criteria to select the most optimal switching alternative for implementation. By employing a pre-selection step, numerous possible switching alternatives can be eliminated before the main selection step is executed, thus reducing the number of possible switching alternatives that subsequently need to be compared. This separation of different selection steps allows for a relatively rapid selection of the most optimal switching alternative, which is then output in a control step via a switching command for implementation in the compressor system.

[0019] Consequently, switching operations can be performed at shorter and more frequent intervals, allowing for improved adaptation of the pressure fluid system to the current conditions of the compressor system. This, in turn, increases the efficiency of compressor operation. For example, if there is a significant withdrawal of pressure fluid from the pressure fluid system, the compressor system control can, by performing a pre-selection step, avoid unnecessarily complex evaluations involving the comparison of a relatively large number of possible switching alternatives using one or more optimization criteria, and can thus limit the evaluation to a smaller number of possible and suitable switching alternatives.Consequently, the present control system is able to react very quickly to a high withdrawal of pressure fluid from the pressure fluid system with a suitable and, if possible, optimal switching alternative.

[0020] Another key concept of the present invention is that the compressor system control system takes measures to reduce the production of compressed pressure fluid when a cut-off pressure is reached, with the cut-off pressure being variable. Accordingly, the present control system differs from a typical pressure band control system known from the prior art, whose upper pressure limit is fixed. The variable design of the cut-off pressure allows for a suitable adaptation of the control action to the current configuration of the compressor system or can also take into account predefined control actions according to a defined change in the configuration of the compressor system.

[0021] Key reasons for the inefficiency of using a compressor system with a typical pressure band control can be twofold: firstly, a pressure band that is set too high can lead to unnecessarily high pressures in the pressure fluid system, causing the compressors under load to perform unnecessary work. Secondly, a pressure band that is set too low can lead to unnecessarily frequent switching of the compressors, resulting in a significant amount of unnecessary work associated with these switching operations.

[0022] In the preceding and following text, the term "switch-on pressure" will be understood as a virtual pressure value at which the compressor system's control unit initiates switching operations to counteract a drop in the overpressure prevailing in the pressure fluid system. The switch-on pressure is therefore lower than the switch-off pressure, which is also defined as a virtual pressure value. At the switch-off pressure, when the actual pressure curve rises, switching operations are also initiated in the compressor system, resulting in the shutdown of compressors. Switching compressors on and off can include not only switching the entire compressor unit on or off to a load cycle, idle cycle, or standstill, but also a gradual change in the delivery rate to higher or lower values.

[0023] According to the switching configuration implemented in the compressor system, the pressure (gauge pressure) within the system changes over time. This pressure profile, which is a measurable quantity, exhibits local minimum and maximum values, resulting from the withdrawal of pressurized fluid from the system and the supply of pressurized fluid by the individual compressors. Typical switching operations performed when the cut-off pressure is exceeded include switching a compressor or compressor group from load to idle or standstill, or reducing the operating time of compressors or compressor groups running under load.Typical switching operations that must be implemented in the compressor system when the lower switching-on pressure compared to the switching-off pressure is exceeded include the load switching of a compressor that is at a standstill or idling, or the increase in the running time of compressors or compressor groups running under load in order to achieve the increased delivery of pressurized fluid.

[0024] Due to the technical design characteristics of compressors, switching operations are essentially implemented immediately when the cut-off pressure is exceeded. However, switching operations that occur when the overpressure in the compressor system decreases and falls below the switch-on pressure are typically implemented only after a certain time delay (dead time). This is because, for example, starting a compressor from standstill or idle to the desired operating speed requires a technically necessary lead time. Accordingly, such lead times are shorter when switching off a compressor compared to switching on a compressor, but both switching operations typically result in a time-shifted implementation of the initiated switching actions.

[0025] Accordingly, in practice, the virtual cut-off pressure is essentially identical to a target virtual upper pressure limit, which in turn is largely identical to the maximum value of the actual pressure curve. Exceptions are possible in cases of very rapid reductions in pressure fluid demand and / or incorrect selection of compressors that are too small to be switched off when not in use, but these are rare in practice. In contrast, the virtual switch-on pressure is generally significantly higher than the target virtual adaptation pressure, which should correspond to the minimum value of the actual pressure curve. This is because, although switching operations are initiated when the switch-on pressure is undershot, these operations can only begin with a time delay due to the inherent delays of the compressors, resulting in full pressure fluid delivery.

[0026] One objective of the present method for controlling a compressor system is to determine the switch-on pressure such that the minimum value of the actual pressure curve reaches the adaptation pressure as closely as possible, but does not fall below it. In other words, the adaptation pressure is a virtual pressure value that the minimum value of the actual pressure curve should reach as closely as possible. The adaptation pressure is thus a target value for a real pressure value that should not be undercut, and which, according to the implementation, is determined variably depending on the current operating state of the compressor system.

[0027] To maintain the pressure resistance limits of the components in the pressurized fluid system, it is typically necessary that the actual pressure profile does not exceed an upper pressure limit. Consequently, suitable switching operations are triggered in the compressor system as soon as the upper pressure limit is reached, such as switching off compressors under load, so that the actual pressure profile does not exceed the upper pressure limit. In practice, the upper pressure limit can generally be set high enough to exceed the cut-off pressures, which are determined based on criteria for minimizing energy consumption. This means that the cut-off pressures and the largely corresponding maximum values ​​of the actual pressure profile are determined primarily or exclusively from an energy efficiency perspective, without influence from the upper pressure limit.

[0028] If the virtual switch-on pressure for individual switching operations is determined on a case-by-case basis in such a way that the real pressure curve reaches the adaptation pressure as accurately as possible when the pressure curve decreases, this has a positive effect on the energy consumption of the entire compressor system, because an unnecessary increase in the pressure level due to premature switching on of compressors is avoided and unnecessary work is not performed.

[0029] It should also be noted that the variable, virtual switch-on pressure is determined by the compressor system's control unit in such a way that the minimum value of the actual pressure curve reaches the specified adaptation pressure as closely as possible, but is not undershot, or only slightly and / or briefly. For this purpose, the switch-on pressure is determined so that the switch-on response time of a compressor or compressor group to be switched on under load follows a predicted pressure curve. The determination of the switch-on or switch-off pressure by the compressor system's control unit can also be carried out on a time basis instead of a pressure basis, in which case the determination of the switch-on or switch-off pressure is replaced by the determination of a suitable switch-on or switch-off time.A control system based on a time basis is therefore equivalent to the existing control system based on a pressure basis. The determination of an activation time, like the determination of an activation pressure (the same applies to an activation time or activation pressure), is performed on a case-by-case basis for future switching operations.

[0030] Furthermore, it should be noted that the method intended for providing a predetermined overpressure in a pressurized fluid system can also be used analogously in a vacuum system in which a non-exceeding negative pressure is to be maintained and made available to users. Switching on a pump within such a system would consequently result in a decrease in the pressure of the pressurized fluid in the system, and switching off a pump or pump group would accordingly result in an increase in the pressure in the pressurized fluid system if vacuum is drawn or if the vacuum deteriorates, e.g., due to leaks.According to expert understanding, the transfer of the present method for controlling a system to maintain a predetermined overpressure to a method for controlling a compressor system in which a predetermined underpressure is not to be exceeded is analogously feasible.

[0031] In a preferred embodiment of the method for controlling a compressor system, it is provided that the control of the system takes measures to increase the generation of compressed pressure fluid when a possibly variable switch-on pressure is reached and measures to reduce the generation of compressed pressure fluid when a possibly variable switch-off pressure is reached.

[0032] In a further preferred embodiment of the method for controlling a compressor system, the cut-off pressure is determined, and in particular calculated, on a case-by-case basis during energy optimization. Accordingly, the compressor systems are primarily controlled with the aim of optimizing, i.e., minimizing, energy consumption, while simultaneously maintaining a predetermined overpressure (adaptation pressure) in the compressor system, i.e., preferably not falling below it, or only to an insignificant degree and / or for a short time. Hereinafter, optimization or minimization is to be understood solely as optimization or minimization within the scope of the possible switching alternatives. Due to this minimization of energy consumption, the present method differs significantly from conventional pressure band control methods, which primarily control the pressure in the pressure fluid system and not the energy consumption of the compressor system.By utilizing the technical degrees of freedom provided by selecting a suitable switching alternative from a multitude of different options, targeted energy savings can be achieved. In particular, the variable switching pressure can be determined such that, if the actual pressure profile falls below the switching pressure, the virtual adaptation pressure at the reversal point of the actual pressure profile corresponds as closely as possible to the minimum value of the actual pressure. Such optimization allows the desired pressure level to be maintained while simultaneously minimizing the number of necessary switching operations, resulting in highly economical operation.

[0033] In a further embodiment of the method according to the invention, the optimal cut-off pressure is determined by computationally minimizing the quotient of the total work loss in a predefined periodic time interval relating to a switching alternative and the time interval itself. Here, the total work loss comprises the sum of the work loss of all compressors running under load in the time interval, the idling work loss of all compressors to be switched on in the time interval, and the switching work loss of all compressors to be switched on and off in the time interval. The periodic time interval is based on the consideration of so-called switching cycles. Such (virtual) switching cycles are time-pressure profiles that repeat themselves in the same (periodic) manner within the time interval (switching cycle duration), rising from a minimum to a maximum and then falling back to a minimum pressure value, which occur at times, i.e.,This would result in essentially constant pressure fluid withdrawal, at least for the duration of the switching cycle. For the sake of simplification, it can be assumed that the pressure fluid withdrawal from the pressure fluid system occurs in such a way that the actual pressure profile between the minimum and maximum pressure values ​​can be considered linear or approximated by straight lines. The compressor(s) to be switched on when the switch-on pressure is reached under load or when the switch-off pressure is reached from load are assumed to be known and can also be selected in advance using suitable heuristics. Furthermore, it is typically assumed that the operating states of the other compressors are only influenced by the profile of the actual pressure and otherwise remain unchanged.

[0034] A switching cycle now encompasses one period of the actual, also periodic, pressure profile. Assuming the simplifying assumptions, the average power consumption of all compressors within the compressor system during a switching cycle, i.e., during the previously described periodic time interval, can be minimized using a closed mathematical expression. However, this does not require considering the total average power consumption of all compressors; instead, a suitably defined total power loss P can be used for simplification. vAssuming a specific value, which will be treated as a representative example, this power loss can be calculated in the simplest case as the quotient of the previously described total energy loss and the length of the periodic time interval of a switching cycle. The total power loss defined in this way is a time-averaged power loss within a switching cycle. As will be explained in detail below, an optimized switching cycle pressure difference can be calculated through simple mathematical manipulation, which can be derived from easily determined parameters. The switching cycle pressure difference is defined as the difference between the cut-off pressure and the adaptation pressure.

[0035] Tests have shown that control methods which use optimization of the switching cycle pressure difference as an optimization criterion have achieved significant success in reducing the energy consumption of the compressor system.

[0036] In a further development of the method according to the invention, it can also be provided that the following quantities are included in the calculation of the cut-off pressure: energy consumption of the compressors running under load, particularly when pumping against a continuously increasing pressure, and / or idling losses of the compressors to be switched to idle or standstill, and / or idling losses of the compressors already idling, and / or switching loss energy of the compressors to be switched for each switching alternative. The relevant quantities can be determined according to known heuristics or by suitable experiments or calculation methods.In particular, they can also quantitatively represent the temporal behavior of individual compressors in the form of time-dependent curves for all load, idle, or switching states, whereby the time delay between a switching point and the complete execution of a switching operation can be explicitly taken into account. The delay times can thus also be included as a calculation parameter in determining a suitable switch-on or switch-off pressure.

[0037] In this embodiment, it is also possible that the switch-on pressure in the method for controlling a compressor system is calculated such that the actual pressure profile reaches a calculated, achievable adaptation pressure, which is below the switch-on pressure, as precisely as possible, preferably with a deviation of less than 5%, further preferably with a deviation of less than 2%, and further preferably not falling below it at all or only insignificantly and / or briefly. Accordingly, the maintenance of a predetermined overpressure in the compressor system can be ensured, while simultaneously achieving economical and efficient control of the compressor system.

[0038] In a further embodiment of the method according to the invention, switching alternatives for reducing the generation of pressure fluid are evaluated according to different optimization criteria than switching alternatives for increasing the generation of pressure fluid. Accordingly, a more differentiated adaptation of the method according to the invention can be carried out, which can, for example, ensure that the actual pressure profile at its reversal points, i.e., its minimum and maximum pressure values, during a switching cycle duration reaches the predetermined adaptation pressure and the cut-off pressure, calculated or determined on a case-by-case basis, primarily according to criteria of energy consumption optimization, as precisely as possible.

[0039] In a further embodiment of the inventive method for controlling a compressor system, switching alternatives for reducing the generation of pressurised fluid are weighed and selected according to optimization criteria that primarily or exclusively take into account the respective total energy expenditure of the various switching alternatives under consideration.

[0040] In a further embodiment, the following factors are considered when calculating the total energy consumption of different switching alternatives: the energy demand of the compressors running under load, the idling losses of the compressors to be switched while idling or at standstill, the idling losses of the compressors already idling, and the switching energy loss of the compressors to be switched for each switching alternative. Since the total energy consumption is calculated and optimized for each operating period of the compressor system and directly influences the selection of a suitable switching alternative, a particularly energy-efficient control of the compressor system is achieved.

[0041] The evaluation and selection of the switching alternative can be performed in real time. Here and in the following, "real time" is understood to mean a timescale that is considerably shorter than the time sequence of two switching alternatives to be implemented. Accordingly, the evaluation and selection of the switching alternative is performed with sufficient speed to accommodate even unexpectedly large changes in the pressure fluid supplied in the pressure fluid system. In other words, the delay caused by the evaluation and selection of the switching alternative does not need to be explicitly considered in the control procedure.

[0042] In another embodiment of the method according to the invention, the cut-off pressure and / or switch-on pressure is determined in real time. Accordingly, the control system can be immediately adapted to the changing operating conditions in the pressure fluid system at a sufficient speed, without fundamentally new operating conditions arising during the time required to determine the cut-off pressure and / or switch-on pressure, which would necessitate the selection of a different switching alternative.

[0043] In a further preferred embodiment of the method according to the invention, the system is controlled by taking into account empirical data from past switching operations (adaptive control). In particular, the control system can determine the switch-on pressure such that the delivery start of a compressor switched on under load occurs sufficiently early to allow the pressure reversal of the actual pressure curve to occur as close as possible to the adaptation pressure. Here, the control method can adaptively learn a switch-on response time for each compressor, which is understood as the time interval between the transmission of a switch-on command to implement a switching alternative and the actual onset of the effect on the actual pressure curve. The switch-on pressure can be selected such that the switch-on response time is equal to the time interval in which the actual pressure curve is expected to drop from the switch-on pressure to the adaptation pressure.This time period can be estimated, for example, by predicting the further pressure trend based on suitable assumptions, such as the assumption of a linearly decreasing pressure trend.

[0044] Adaptive learning of the switch-on response time for each compressor can be achieved, among other things, by evaluating the actual pressure profiles over several selected periodic time intervals of the actual pressure profile of a compressor or compressor group. The adaptively learned switch-on response times can also be continuously updated by suitable revaluation, for example, by moving average calculation.

[0045] The adaptive learning behavior of the controller significantly supports the goal of optimizing the energy consumption of the compressor system. This adaptive behavior is typically based on underlying learning algorithms and adaptive parameters, which are simulated during the control process and updated by the controller for each subsequent evaluation and selection of a switching alternative. Consequently, the adaptive learning behavior allows the controller to automatically adjust to all control-related properties and conditions of the compressor system during operation. Since application-relevant parameters (energy consumption) can also be recorded and evaluated, the controller flexibly adapts to the behavior of the compressor system during operation, thus optimizing energy consumption.

[0046] The underlying learning algorithms can calculate the specified adaptive variables either by evaluating a measurement tracked over a longer period or by evaluating a suitable number of individual events. Both approaches are suitable for tracking the adaptive variables during the ongoing operation of the compressor system while excluding short-term or singular influences from the calculation of the adaptive variables.

[0047] The adaptive behavior of the control system allows for operation with relatively few control parameters. This eliminates the need for manual optimization or re-optimization of the control behavior, and no further adjustments are required even when the compressor system is expanded or modified. The primary control parameter is typically the adaptation pressure, while the cut-off pressure and the switching pressure differential are determined by criteria aimed at minimizing energy consumption. Consequently, the operational and maintenance effort for commissioning and operating the control system is minimal.

[0048] In a further embodiment of the method according to the invention, the empirical parameters include the energy requirement (energy requirement per fluid quantity) of individual compressors or certain combinations of compressors and / or switching response times of the compressors and / or consumption behavior of the pressure fluid consumers and / or size of the pressure storage tank and / or pressure compensation degree of the compressors or certain combinations of compressors.

[0049] The energy demand ratio, as an adaptive variable, describes the energy efficiency of individual compressors or combinations of compressors during operation and is expressed as the ratio of energy consumption to the fluid volume delivered by the compressors involved. Here, the energy consumption and the fluid volume delivered are calculated by numerically integrating the power input and / or flow rate, respectively, which are made available through computation and / or measurement, over a suitably selected period. Since the calculation of the energy demand ratio describes all actual work performed (loaded work, idling, energy losses, switching losses) as well as the actual fluid volume delivered with sufficient accuracy, it can, unlike values ​​calculated purely from theoretical nominal data of the compressors, reflect the actual energy utilization during operation relatively accurately.

[0050] In this context, it is also possible to take into account in the control system that for compressors and groups of compressors that have a correspondingly low energy utilization due to energy-unfavorable load cycles in the past, and which may be unjustifiably given lower priority in the long term when selecting the units to be switched on (positive feedback), the energy demand is gradually adjusted to the current energy utilization characteristics of the compressor system by means of a compensation mechanism.

[0051] It should also be added that when switching to load, compressors that are idling and have a relatively high residual idle energy are typically preferred over compressors whose motor is already switched off, in order to save energy by avoiding idle and start-up losses. Furthermore, when switching off load, those compressors of the same or similar size with a lower expected residual idle energy loss are typically preferred, consequently saving energy by avoiding idle energy.

[0052] The pressure-related effect of the individual compressors on the control system is described as an adaptive variable in the form of the compressor pressure compensation degree, and can be determined by averaging the pressure compensation effect of switching operations over a suitable number of individual events. The pressure compensation effect of the switching operations can be derived from the pressure profile over time.

[0053] Since the selection of compressors to be switched preferably only considers compressors or groups of compressors whose pressure compensation effect (sum of the pressure compensation degrees) is adapted to the current operating state (current pressure profile) of the compressor system, switching the selected compressors typically establishes the desired pressure profile in a timely manner, so that practically no additional, energetically disadvantageous switching operations are required.

[0054] In operating conditions characterized by rapid changes in pressure drop, compressors may be selected whose pressure compensation effect cannot fully counteract the actual pressure curve by reversing the pressure direction. This results in undercompensation of the actual pressure curve at the switching point. Therefore, in such cases, the switching point can be advanced by a time interval adapted to the degree of undercompensation. A time buffer is provided to switch additional compressors in a timely manner if needed. This ensures that, ideally, no further compressors need to be switched, or at least that after a switchover, the pressure can be stabilized at an energy-efficient level for a relatively long period.

[0055] Furthermore, in very rare cases, under conditions of strong fluctuations in the compressed air draw from the compressor system, the adaptation pressure may fall below an acceptable level. In such situations, the control system can, if necessary, immediately and appropriately counteract the deviation of the actual pressure profile from the adaptation pressure by immediately switching one or more additional compressors into load. Even during the ongoing switch-on process, i.e., before the pressure compensation effect of the switched-on compressors has taken effect, the system can check the actual pressure profile to determine whether the future pressure compensation effect is likely to be sufficient to establish the desired actual pressure profile. If the future pressure compensation effect is determined to be sufficient, no further compressors are switched into load.In the opposite case, one or more compressors are immediately switched to load.

[0056] In an alternative embodiment of the method according to the invention, the empirical parameters can include the following: the pressure compensation degree of a compressor as a function of the storage volume and the installation scheme of the pressure fluid system, and / or the energy consumption degree of a compressor as a function of its previous operating mode, its ambient temperature, its maintenance, wear, and contamination status, and / or its switch-on response time, and the pressure compensation degree of a compressor as a function of typical patterns of changes in pressure fluid withdrawal. Accordingly, the control system can adaptively learn not only purely compressor-specific properties, but also, in part, properties that result from the interaction of compressors and the operating state or the respective operating environment.

[0057] In a further preferred embodiment of the method according to the invention, it is characterized in that the activation of compressors or combinations of compressors is carried out in such a timely manner that, taking into account the start-up behavior of the compressor or compressor combination, and in particular taking into account preferably adaptively learned activation response times, the actual pressure profile reaches the adaptation pressure as precisely as possible, preferably with a deviation of less than 5%, more preferably with a deviation of less than 2%, and more preferably does not fall below it, or only insignificantly and / or briefly. Accordingly, the actual pressure profile, at its minimum pressure value, reaches the virtually determined adaptation pressure as precisely as possible within relatively narrow limits.

[0058] In a further embodiment of the method according to the invention, it can be provided that, when determining the switching alternatives for the compressors to be switched under load, those compressors or combinations of compressors are preferably selected that exhibit favorable values ​​of empirical parameters for energy efficiency. This ensures the most energy-efficient operation of the compressor system possible.

[0059] In another embodiment of the method for controlling a compressor system, when determining the switching alternatives, compressors to be switched under load are preferably selected that are idling and have a long remaining idle time, and / or compressors to be switched to idle or standstill are preferably selected that have a low residual idle energy. Accordingly, the total energy loss, as the sum of all energy losses, is also reduced, since a reduction in residual idle energy is taken into account when determining the switching alternative to be selected, in the sense of energy optimization.

[0060] In a further preferred embodiment of the method according to the invention, the determination of switching alternatives and / or the determination of a switch-off pressure and / or the determination of an activation pressure is carried out under the assumption of a constant pressure fluid decrease. Here, the assumption of a constant pressure fluid decrease is sensibly applied only for determining the next activation or switch-off pressure. For the subsequent determination of a future activation or switch-off pressure, a new, again constant, value for the pressure fluid decrease is optionally assumed. This assumption of a constant pressure fluid decrease allows the actual pressure profile during a switching cycle, including the next activation process, to be calculated in terms of energy consumption using mathematically simple expressions.Consequently, an energy optimum or maximum efficiency with regard to the operation of the compressor system can also be calculated for the duration of a switching cycle.

[0061] In a further embodiment of the method according to the invention, the determination of a current value of the pressure fluid withdrawal is either determined by a measuring device, calculated from the actual pressure profile over time, the operating state of the compressors and / or the optionally adaptively learned storage size of the compressor system.

[0062] In a further embodiment of the method according to the invention, it is characterized in that, under predetermined conditions, the activation or deactivation commands to be triggered upon reaching the activation or deactivation pressure are suppressed and / or additional activation or deactivation commands can be triggered independently of reaching the activation or deactivation pressure. For example, additional deactivation commands can be triggered when approaching the upper pressure limit to prevent the actual pressure profile from exceeding the upper pressure limit. Furthermore, if there is a significant and sustained positive curvature in the decreasing pressure profile due to a decreasing pressure fluid withdrawal from the pressure fluid system, a determined activation command can be suppressed to allow for a better estimation of the subsequent actual pressure profile.Consequently, shutdown commands can also be suppressed in the case of a significant and sustained negative bend in an increasing actual pressure curve, which results from increasing pressure fluid withdrawal. Here, too, to perform an improved energy calculation, the switching alternative selected by the controller is initially suppressed in order to better estimate the further pressure curve and, consequently, to be able to execute a switching operation in the future with improved energy consumption.

[0063] In another preferred embodiment of the method according to the invention, when determining several switching alternatives as energetically equivalent, other criteria are additionally taken into account in the selection, such as the number of operating hours of a compressor under consideration. Accordingly, it can be ensured that the number of operating hours of different compressors included in the compressor system is largely uniform, thereby reducing maintenance-related or usage-related failures of individual compressors to a predetermined level.

[0064] According to a further embodiment of the method according to the invention, the determined shutdown is only released by the control system if it is ensured that any necessary switching operation can be carried out in a timely manner, taking into account the start-up behavior of a possible switching combination. By considering the start-up behavior of a compressor or a combination of compressors in the compressor system in this way, the provision of a predetermined overpressure in the pressure fluid system can always be maintained. An unforeseen and, under normal circumstances, energy-inefficient switching on of further compressors or compressor groups due to the release of a determined switching operation that cannot be implemented in time can thus be avoided.

[0065] Further embodiments of the invention are set out in the dependent claims.

[0066] The invention is described below using exemplary embodiments, which are explained in more detail with reference to the illustrations.

[0067] This shows: Fig. 1 a schematic representation of a compressor system comprising a plurality of compressors; Fig. 2 a schematic representation of an embodiment of the control device according to the invention for controlling the in Fig. 1 compressor system shown; Fig. 3 a schematic representation of an embodiment of the control system according to the invention in flowchart form; Fig. 4 a representation of a real pressure profile in a compressor system specifying particular control variables according to an embodiment of the control method according to the invention;

[0068] Fig. Figure 1 shows a schematic representation of a compressor system 1, which comprises a total of six compressors 2, each connected to a communication bus 5. Each compressor 2 is connected via suitable pressure lines to treatment elements 21, which can be configured, for example, as dryers or filters. The six compressors 2 supply a central pressure fluid reservoir 3, which also includes a measuring device 20 that is likewise connected to the communication bus 5. The measuring device 20 allows, for example, continuous measurement of the pressure in the pressure fluid reservoir 3 and can transmit measurement parameters via the communication bus 5 to the control system of the compressor system 1, which are available for control engineering purposes in the control method 41 (not shown here).

[0069] The pressurized fluid supplied to the pressure fluid reservoir 3 by the compressors 2 is conveyed to a user for dispensing via a suitable pressure line, which may alternatively include further functional elements 22 (in this case, for example, a control valve). The overpressure maintained in the pressure fluid reservoir 3 is controlled by a central control unit 4, which is not shown here, but which is in communication communication with the communication bus 5. Communication between the compressors 2 and the communication bus 5 can take place via conventional signal wiring or wirelessly.

[0070] As implemented, the selected communication protocol can ensure the real-time execution of the control procedure, which is described in greater detail below. The pressure prevailing in the pressure fluid reservoir 3 is also preferably measured in real time by the measuring device 20. In practical terms, sampling at time intervals of less than one second, preferably less than one-tenth of a second, is suitable for this purpose. In typical pressure fluid applications, the measuring device 20 measures an overpressure in the pressure reservoir 3. In vacuum applications, which are also possible, as described above, the measuring device 20 measures a corresponding underpressure, which can also be provided in the pressure fluid reservoir 3. As is understandable to those skilled in the art, the compressors 2 are replaced by suitable vacuum pumps for this purpose.The pressure value recorded by the measuring device 20 can be smoothed to a greater or lesser extent depending on the intended use, and evaluated absolutely, differentially over time, or combinatorially in order to be introduced into the control procedure. The pressure value thus conditioned can be used, among other things, for calculating an energetically optimal cut-off pressure 103 (not shown here), for calculating a pressure compensation factor of the compressors, and for calculating the switch-on response times of the compressors when stationary or idling.

[0071] In addition, a further measuring device can be provided, which is also connected to the central control unit and determines the measured pressure fluid consumption or pressure fluid withdrawal in order to determine switching response times with higher accuracy.

[0072] The operating data of the compressors, exchanged with the central control unit via communication bus 5, includes, among other things, the current operating status of each compressor. This information is required by the control system for selecting which compressors to switch to load. Furthermore, this information includes the motor speed, which the control system uses to determine the energy consumption of a compressor or compressor group. Additionally, this information can include data from internal compressor pressure sensors for determining run-on times when the compressor is idling, or predicted run-on times when the compressor is under load, as well as information about whether the compressor is actually operating under load.Alternatively, some or all of the aforementioned operating data of the compressors can also be simulated or approximated in the control procedure using data technology, so that they do not have to be exchanged via the communication bus 5 and are still available to the central control unit in a sufficiently approximate manner.

[0073] The compressor system 1 may also include, for application-related reasons, conditioning elements 21 that cause a characteristic change in the system's internal fluid pressures. However, the influence of the conditioning elements 21 in the compressor system 1 can be appropriately compensated for by suitable adaptive learning behavior of the control system. For example, an increasing time delay in the pressure fluid delivery between a compressor and the central pressure fluid reservoir due to an increasingly dirty filter can be adaptively compensated for by an increasing switch-on response time of the compressor from the off state and from the idle state. Such an extended switch-on response time can easily be compensated for by the control system, so that the increasing filter contamination does not adversely affect the maintenance of the predetermined overpressure in the pressure fluid reservoir 3.

[0074] Furthermore, the present compressor system 1 may, due to application-related considerations, have one or more pressure regulating valves for pressure stabilization.

[0075] Fig. Figure 2 shows a schematic representation of the control procedure of the control unit 4. The control unit 4 is in communication contact with the communication bus 5 and can both read and receive information. In particular, the control unit 4 can transmit switching commands to individual compressors 2 via the communication bus 5. For supplying control parameters or inputting data for characterizing the compressors 2, the control unit 4 includes a data input interface 40. This data is passed on to the control procedure 41, which can be implemented as a software application, for example, as an adaptive control procedure. The control procedure 41 generates suitable control commands or switching commands for controlling the compressors 2, which are transmitted to the compressors 2 via the communication bus 5.The control method 41 includes a control algorithm 42, which regulates the energy demand of the compressor system within a pressure range (switching cycle pressure differential). It should be noted that the control algorithm 42 can also be understood as a control algorithm. Furthermore, the control device 4 includes a system clock (not shown here) with a suitable clock generator, which can provide the control method 41 with a suitable time reference.

[0076] As implemented, the control algorithm 42 enables energy-driven adaptive control and determines an energy-efficient cut-off pressure 103 for the compressors to be switched off from load within the available pressure range. For this purpose, the control algorithm 42 calculates the energy-optimal cut-off pressure 103 in mathematically analytical form. This optimal cut-off pressure 103 is defined as the minimum value of the switching cycle pressure difference according to a function that describes the power loss of all compressors 2 of the compressor system 1 during a switching cycle as a function of the cut-off pressure 103. The calculation assumes that the average pressure drop remains constant and that, therefore, the switching cycle repeats itself identically with respect to the average pressure changes between two successive minimum and maximum pressure values.By assuming a constant average pressure fluid withdrawal rate, fluctuations in the pressure profile can also be taken into account in the actual pressure profile.

[0077] The energy-driven control algorithm 42 utilizes existing control engineering degrees of freedom by not restricting these degrees of freedom through fixed control parameters or, for example, a pressure control range that is too small or rigidly defined, but rather by optimizing them from an energy perspective. Neither the selection of the compressors 2 to be switched nor the timing or pressures for the switching operations are parameterized, but are calculated by the control method 41 on a case-by-case basis with energy optimization in mind.

[0078] In addition to the energy management of the control method 41, this method is also characterized by adaptive behavior with regard to the adjustment of adaptive parameters during operation. This adaptive behavior significantly supports the optimization of the energy consumption of the compressor system 1. The adaptive behavior is based on an adaptation algorithm 43 included in the control method 41, which tracks all adaptive parameters during the operation of the compressor system and makes them available to the control algorithm 42. The adaptive behavior also allows for the automatic adjustment of the selection of compressors to be switched to all control-related, fixed and variable properties or conditions of the compressor system and the application during operation.Examples of such adaptive variables can be the energy requirement per unit of fluid delivered by a compressor 2 or a combination of compressors 2 during operation, as well as the pressure-effective storage volume of the pressure fluid system and the time-dependent switching behavior of the compressors 2.

[0079] Fig. Figure 3 shows a schematic representation of the sequence of individual steps according to an embodiment of the inventive method for controlling a compressor system 1 in flowchart form. In a preselection step 10, certain switching alternatives 13 are excluded from the multitude of combinatorially available switching alternatives 13 in an exclusion device 6 of a control device 4 (not shown), preferably taking into account the current conditions. The preselection can, for example, be based on selection criteria that consider the technical feasibility of the predetermined switching alternatives 13. In this case, for example, a total of eight combinatorially possible switching alternatives 13 are available, of which four switching alternatives 13 (deselected by cross-pollination) have proven unsuitable for the present operating conditions and are therefore preselected.From the remaining four switching alternatives 13, a switching alternative 13 is selected in a main selection step 11 in a selection device 7 of the control device 4 (not shown) by applying one or more optimization criteria, by weighing all switching alternatives 13 not deselected in the pre-selection step 10 against each other. The selected switching alternative 13 determined in the main selection step 11 is output in a control step in an output device 8 of the control device 4 (not shown) for implementation in the compressor system 1. For illustrative purposes, the output has been represented here as the forwarding of information from the output device 8 to the communication bus 5, which, however, should not be understood as a limitation in this context.

[0080] Fig. Figure 4 shows a representation of the real pressure profile 105 in the pressure fluid system during a periodic time interval T. Schalt The length of the periodic time interval T SchaltThis specifically concerns the length of a switching cycle. According to one embodiment of the control method according to the invention, the control system determines an individual cut-off pressure 103 for the compressors 2 to be switched off from load within the available pressure range according to principles of energy optimization. The pressure range (switching cycle pressure differential) is the pressure range between a cut-off pressure 103 and an adaptation pressure 101 that must not be exceeded. In this embodiment, the energy-optimal switching cycle pressure differential and the energy-optimal cut-off pressure 103 for the compressors 2 to be switched off from load are calculated mathematically and analytically as an energy optimum. For this calculation, it is assumed that the pressure drop is constant on average. The pressure drop can therefore be represented as the slope of a linearly decreasing line, which approximately describes the actual pressure profile.Similarly, the pressure fluid increase in the pressure fluid system can be described as a monotonically increasing straight line by a largely similar mathematical averaging of the actually increasing pressure profile.

[0081] Under these conditions of a constant average pressure fluid withdrawal, the switching cycle, including the next switching operation, can be energetically described by a simple mathematical representation. Based on this simple mathematical representation, it is possible to calculate the energy optimum or the maximum efficiency of the compressor system during such a switching cycle. For this purpose, the control method 41 regulates the switch-off pressure 103 of the compressors 2 to be switched such that the total power loss dependent on the switching cycle (total work loss per periodic time interval T) is Schalt ) becomes minimal.

[0082] Both the load-running and the switching and idling compressors 2 contribute to this switching-cycle-dependent power loss. The energy demand of the load-running compressors (load work) increases with the switching-cycle pressure differential because their average internal operating pressure differential increases. In contrast, however, the switching-cycle and idling-cycle power losses of the switching compressors decrease with increasing switching-cycle pressure differential, as the number (frequency) of switching cycles decreases. With the calculated switching-cycle pressure differential, the sum of the loss components reaches a minimum during energy optimization. The expression to be minimized is given by the following equation (1): PV=(ΔWload+ΔWempty+ΔWswitch) / TSwitch

[0083] Here, ΔW Last The energy loss of the load-running compressors per switching cycle due to the pressure increase compared to the switch-on pressure, ΔW LeerThe idle energy loss of the compressors to be switched per switching cycle due to their idle power and their run-on time, ΔW Schalt The switching energy loss per switching cycle of the compressors to be switched 2 due to the slow internal pressure equalization process when switching to idle, possibly a motor restart and the internal pressure equalization when switching to load, T Schalt the switching cycle duration, which extends over a periodic pressure increase and the subsequent pressure drop.

[0084] The individual components of the total energy loss are calculated according to equation (2): ΔWLast=0.5⋅rLast⋅ΔpSwitch2⋅(PLast1 / Idp / dtlmittel1+PLast2 / Idp / dtlmittel2)

[0085] Here, r Last the relative increase in the load power of the load-running compressor 2 per pressure unit, Δp Schalt the shifting pressure differential, P Last1the load power of the compressors running under load during the pressure curve towards the cut-off pressure 103, including the compressors to be switched on 2, at the switch-on pressure 102, Idp / dtl mittel1 the amount of the expected average pressure increase during the actual pressure curve towards the cut-off pressure 103, calculated on the basis of a reasonable period, P Last2 the load power of the compressors 2 running under load during the pressure curve towards the switch-on pressure 102, excluding the compressors 2 to be switched on, at the switch-on pressure 102, ldp / dtl mittel2 the magnitude of the expected mean pressure gradient during the pressure profile in the direction of the switch-on pressure 102 from ldp / dtl mittel1 and the pressure compensation effect of the compressors to be switched 2.

[0086] The idle energy loss ΔW Leer is calculated based on the following equation (3): ΔWLeer=∑(PLeer⋅TLeer)

[0087] Here, P Leer the idle power of the individual compressors to be switched and T Leer The idle run time of each individual compressor to be switched is limited to the time between switching off and switching on.

[0088] The switching loss ΔW Schalt is calculated as the sum of the switching losses W Schalt per switching cycle of the compressors to be switched 2 according to the following equation (4): ΔWShift = ∑WShift

[0089] Furthermore, the periodic time interval T Schalt a switching cycle can be easily calculated based on the following relationship according to equation (5), which can be derived from simple geometric considerations according to Fig. 4 equals: TSwitch=ΔpSwitch⋅(1 / ldp / dtlmittel1+1 / ldp / dtlmittel2)

[0090] Calculation of the energetically optimal switching cycle pressure difference Δp Schalt,optThis can be achieved using equation (1) by simply substituting the terms for the individual work losses ΔW. Last , ΔW Leer , W Schalt as well as the length of the periodic time interval (switching cycle duration) T Schalt into the formula according to equation 1 for the power loss P that depends on the switching cycle v , by subsequent derivation according to the switching cycle pressure difference Δp Schalt and calculate the corresponding zeroing of the derivative. Consequently, the energetically optimal switching cycle pressure difference Δp can be calculated. Schalt,opt represent as a mathematically easy-to-handle expression according to equation (6): ΔPswitch=√{[∑(PLeer⋅TLeer)+∑WSwitch] / [0.5⋅rLast⋅(PLast1 / ldp / dtlmittel1+PLast2 / ldp / dtlmittel2)]

[0091] The energetically optimal cut-off pressure in pressure fluid applications is the sum of the adaptation pressure 101 and the calculated energetically optimal switching cycle pressure difference Δp. Schalt,optIn appropriate vacuum applications, for example, the energetically optimal cut-off pressure 103 is the difference between the two previously mentioned values, as is understandable to a specialist.

[0092] Furthermore, it should be noted that the implemented control method takes into account the delay times of the individual compressors 2 or combinations of compressors 2, which are determined by the times between switching on or off a compressor 2 and the times of the actual implementation of the change of state. Accordingly, the switching times T are also zu how the shutdown times T ab compared to the minimum pressure values ​​of the actual pressure curve 105 or compared to the maximum pressure values ​​shifted forward in time.

[0093] Furthermore, in Fig.Figure 4 shows a partially idealized switching cycle for illustrative purposes. An upper pressure limit 104 is determined by the system, for example, by the pressure resistance of the components. The lowest line in the diagram represents the adaptation pressure 101, which has already been discussed several times. In the switching cycle shown here, the pressure profile moves between a (local) minimum value P min and a (local) maximum value P max At a time T AB , namely when the cut-off pressure 103 is reached during an increasing pressure curve, measures are taken to reduce the generation of compressed pressure fluid, which have the effect that the pressure briefly exceeds the cut-off pressure 103 to the (local) maximum value P maxThe pressure rises, but then reverses into a pressure drop. As soon as the cut-in pressure of 102 is reached during the decreasing pressure curve, measures are taken to increase the generation of compressed pressure fluid, so that the pressure is reduced even further to a (local) minimum value P. min The pressure drops, but then the pressure drop reverses into a renewed pressure increase.

[0094] It should be noted here that all parts described above, whether considered individually or in any combination, and in particular the details shown in the drawings, are claimed to be essential to the invention. Modifications to this are familiar to those skilled in the art. Reference symbol: 1 compressor system 2 compressor 3 Pressure fluid reservoir 4 Control unit 5 Communication bus 6 Exclusion device 7 Selection facility 8 Output device 9 Shut-off pressure detection device 10. Pre-selection step 11 Main Selection Step 12 Control Step 13 switching alternatives 20 Measuring device 21 Processing element 22 Functional element 30 data sets 40 Feed interface 41 Control methods 42 Control algorithm 43 Adaptation algorithm 101 Adaptation pressure 102 Switch-on pressure 103 Cut-off pressure 104 upper pressure limit 105 actual pressure profile T zu Switch-on time T ab Shutdown time

Claims

[1] Method for controlling a compressor system (1) comprising a plurality of compressors (2), in particular of different designs and / or capacities, wherein the compressor system (1) is intended to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, where decisions are made at fixed or variable time intervals regarding switching operations to adapt the pressure fluid system to current conditions, that - in a pre-selection step (10), taking into account the current conditions, switching alternatives (13) are excluded from the multitude of combinatorially available switching alternatives (13), - in a main selection step (11) remaining switching alternatives (13) are weighed against each other using one or more optimization criteria and optimal switching alternatives (13) are selected under the given criteria and - in a control step (12) the selected switching alternative (13) is output for implementation in the compressor system (1) characterized by , that the control of the system (1) takes measures to increase the generation of compressed pressure fluid when a potentially variable switch-on pressure (102) is reached and measures to reduce the generation of compressed pressure fluid when a potentially variable switch-off pressure (103) is reached, wherein The optimal cut-off pressure (103) is determined by computationally minimizing the quotient of the total work loss in a predefined periodic time interval relating to a switching alternative (13) and the time interval itself, wherein the total work loss includes the sum of the work loss of all load-running compressors (2) in the time interval, the idle work loss of all compressors (2) to be switched on in the time interval, and the switching work loss of all compressors (2) to be switched on and off in the time interval. [2] Method for controlling a compressor system (1) comprising a plurality of compressors (2), in particular of different designs and / or capacities, wherein the compressor system (1) is intended to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, wherein The control system of the system may take measures to increase the generation of compressed pressure fluid when a potentially variable switch-on pressure (101) is reached and measures to reduce the generation of compressed pressure fluid when a switch-off pressure (103) is reached, in particular according to claim 1, where the cut-off pressure (103) is variable, wherein the cut-off pressure (103) is changed depending on the current configuration of the compressor system (1) and / or taking into account a defined switching operation (a defined change in the configuration of the compressor system), characterized by , that the optimal cut-off pressure (103) is determined by computational minimization of the quotient of the total work loss in a predefined periodic time interval relating to a switching alternative (13) and the time interval itself, wherein the total work loss includes the sum of the work loss of all load-running compressors (2) in the time interval, the idle work loss of all compressors (2) to be switched on in the time interval and the switching work loss of all compressors (2) to be switched on and off in the time interval. [3] Method according to claim 1 or 2, characterized by , that the cut-off pressure (103) is determined on a case-by-case basis in an energy optimization, in particular calculated. [4] Method according to any one of claims 1 to 3, characterized by , that the optimal cut-off pressure (103) is based on the following formula ΔPswitch=√{[∑(PLeer⋅TLeer)+∑WSwitch] / [0.5⋅rLast⋅(PLast1 / ldp / dtlmittel1+PLast2 / ldp / dtlmittel2)] is calculated. [5] Method according to claim 3, characterized by , which is included in the calculation of the cut-off pressure (103): - Energy demand of the compressors running under load (2), especially when pumping against a steadily increasing pressure and / or - Idle losses of the compressors that are switched to idle or standstill and / or - Idle losses of the compressors while idling and / or - Switching loss energy of the compressors to be switched per switching alternative (13). [6] Method according to any one of claims 1 to 5, characterized by, that the switching pressure (102) in the method for controlling a compressor system (1) is calculated such that the actual pressure profile reaches a predetermined, achievable adaptation pressure (101), which is below the switching pressure (102), as accurately as possible, preferably with less than 5%, further preferably with less than 2% deviation, and further preferably does not fall below it or only falls below it insignificantly and / or briefly. [7] Method according to any one of claims 1 to 6, characterized by , that switching alternatives (13) for reducing the generation of pressure fluid are evaluated according to different optimization criteria than switching alternatives (13) for increasing the generation of pressure fluid. [8] Method according to any one of claims 1 to 7, characterized by, that the consideration and selection of switching alternatives (13) for reducing the generation of pressure fluid are made under optimization criteria which take into account primarily or exclusively the respective total energy expenditure of the various switching alternatives (13) under consideration. [9] Method according to claim 8, characterized by , that when considering the total energy expenditure of different switching alternatives (13) at least the following is taken into account: - Energy demand of the compressors running on load and / or - Idle losses of the compressors that are switched to idle or standstill and / or - Idle losses of the compressors while idling and / or - Switching loss energy of the compressors to be switched per switching alternative (13). [10] Method according to any one of claims 1 to 9, characterized by , that the assessment and selection of the switching alternative (13) take place in real time. [11] Method according to any one of claims 1 to 10, characterized by , that the determination of the cut-off pressure (103) and / or switch-on pressure (102) takes place in real time. [12] Method according to any one of claims 1 to 11, characterized by , that the control of the system (1) is carried out taking into account empirical data from past switching operations (adaptive control). [13] Method according to claim 12, characterized by , that the empirical data include: - Energy demand (energy demand per fluid quantity) of individual compressors (2) or certain combinations of compressors (2) and / or - Compressor activation response times (2) and / or - Consumption behavior of the pressure fluid consumers and / or - Size of the pressure reservoir and / or - Pressure compensation degree of the compressors (2) or certain combinations of compressors (2). [14] Method according to one of claims 12 or 13, characterized by, that the empirical data include: - Pressure compensation degree of a compressor (2) depending on the storage volume and the installation scheme of the pressure fluid system and / or - Energy consumption of a compressor (2) depending on its previous operating mode, its ambient temperature, its maintenance, wear and contamination status and / or - Switch-on response time and pressure compensation degree of a compressor depending on typical patterns of change in the withdrawal of pressurized fluid. [15] Method according to any one of the preceding claims, characterized by, that the activation of compressors (2) or combinations of compressors (2) is carried out in such a timely manner that, taking into account the start-up behavior of the compressor (2) or the compressor combination, in particular taking into account preferably adaptively learned activation response times, the actual pressure profile reaches the adaptation pressure (101) as accurately as possible, preferably with less than 5%, further preferably with less than 2% deviation, and further preferably does not fall below it or only falls below it insignificantly and / or briefly. [16] Method according to any one of claims 1 to 15, characterized by , that when determining the switching alternatives (13) as compressors (2) to be switched in load, preferably those compressors (2) or combinations of compressors (2) are selected which have favorable values ​​of empirical values ​​for the energy demand level. [17] Method according to any one of claims 1 to 16, characterized by, that when determining the switching alternatives (13) as compressors (2) to be switched under load, preferably those compressors (2) are selected which are in idle mode and still have a large residual idle time, and / or for compressors (2) to be switched in idle or standstill, preferably those compressors (2) are selected which have a low residual idle work. [18] Method according to any one of claims 1 to 17, characterized by , that the determination of switching alternatives (13) and / or the determination of a cut-off pressure (103) and / or the determination of a switch-on pressure (102) are carried out under the assumption of a constant pressure fluid decrease. [19] Method according to any one of claims 1 to 18, characterized by, that the determination of a current value of the pressure fluid withdrawal is either determined by a measuring device or calculated from the actual pressure profile over time, the operating state of the compressors (2) and / or the possibly adaptively adjusted storage size of the compressor system (1). [20] Method according to any one of claims 1 to 19, characterized by , that under predetermined conditions the switching commands or switching commands to be triggered upon reaching the switching pressure (102) or switching pressure (103) are suppressed and / or additional switching commands or switching commands can be triggered independently of reaching the switching pressure (102) or the switching pressure (103). [21] Method according to any one of claims 1 to 20, characterized by, that when determining several switching alternatives (13) as being energetically equivalent, other criteria are additionally taken into consideration in the selection, such as the number of operating hours of a compressor under consideration (2). [22] Method according to any one of claims 1 to 21, characterized by , that a detected shutdown is only released by the control system if it is ensured that any necessary switching-on process can be carried out in a timely manner, taking into account the start-up behavior of a possible switching combination. [23] Control device (4) for a compressor system (1) comprising a plurality of compressors (2), in particular of different design and / or performance, for carrying out a method according to one of claims 1 to 22, wherein the compressor system (1) is intended to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, wherein decisions on switching operations are made at fixed or variable time intervals to adapt the pressure fluid system to current conditions and wherein the control device comprises - an exclusion device (6) which, taking into account the current conditions, excludes switching alternatives (13) from the multitude of combinationally available switching alternatives (13), - a selection device (7) that weighs the remaining switching alternatives (13) against each other using one or more optimization criteria and selects an optimal switching alternative (13) from among the specified criteria, as well as - an output device (8) designed to output the selected switching alternative (13) for implementation in the compressor system. [24] Control device (4) for a compressor system (1) comprising a plurality of compressors (2), in particular of different design and / or performance, for carrying out a method according to one of claims 1 to 22, wherein the compressor system (1) is intended to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, and wherein the control device (4) comprises a cut-off pressure determination device (9) which determines a cut-off pressure (103) in the event of an overproduction of pressure fluid depending on the current configuration of the compressor system and / or taking into account a defined switching operation (a defined change in the configuration of the compressor system). [25] Data set (30), preferably configured for transmission in a data network or stored on data carriers, for controlling a compressor system (1) for carrying out a method according to one of claims 1 to 22, wherein the compressor system (1) comprises a plurality of compressors (2), in particular of different designs and / or capacities, wherein the compressor system (1) is intended to maintain a predetermined overpressure in a pressure fluid system despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, where decisions are made at fixed or variable time intervals regarding switching operations to adapt the pressure fluid system to current conditions, that - in a pre-selection step (10), taking into account the current conditions, switching alternatives (13) are excluded from the multitude of combinatorially available switching alternatives (13), - in a main selection step (11) remaining switching alternatives (13) are weighed against each other using one or more optimization criteria and optimal switching alternatives (13) are selected under the given criteria and - in a control step (12) the selected switching alternative (13) is output for implementation in the compressor system. [26] Data set (30), preferably configured for transmission in a data network or stored on data carriers, for controlling a compressor system for carrying out a method according to one of claims 1 to 22, wherein the compressor system comprises a plurality of compressors, in particular of different designs and / or capacities, wherein the compressor system in a pressure fluid system is intended to maintain a predetermined overpressure despite potentially fluctuating withdrawal of pressure fluid from the pressure fluid system, wherein The control system (1) may take measures to increase the generation of compressed pressure fluid when a potentially variable switching pressure (102) is reached and measures to reduce the generation of compressed pressure fluid when a switching pressure (103) is reached, in particular according to claim 1, where the cut-off pressure (103) is variable, characterized by , that the cut-off pressure (103) is changed depending on the current configuration of the compressor system (1) and / or taking into account a defined switching operation (a defined change in the configuration of the compressor system).

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